Fig. 4.

Sperm swim upstream and T. foetus are swept away by a gentle flow. (A) At 1 μL/min flow, sperm trajectories are similar to the case in which there is no flow. (B) At 2 μL/min flow, sperm swim against the flow. (C) Almost all (but one) T. foetus are swept downstream by a 1 μL/min flow. (D) A gentle flow of 1 μL/min has very limited impact on the motility of sperm, because the difference in speeds is not statistically significant (P = 0.25). (E) Motility of T. foetus is significantly altered by the presence of a flow. The higher speed in the presence of the flow is due to the fact that T. foetus were passively swept away by the flow. Flow speed in the channel has a Poiseuille profile across the vertical direction and ranges from 6 to 86 μm/s. T. foetus is distributed along the vertical direction in the channel. Number of cells analyzed is 50. Error bars show SEM.